You configure each circuit for VLAN or S-VLAN subinterfaces that you create across
a set of candidate Ethernet ports. The router distributes traffic from the core through
the candidate ports used by the load-balancing group. If a port is disabled, traffic is
redistributed to a working port.
MPLS Interfaces and Labels
When a layer 2 interface is added to a load-balancing group circuit, an MPLS shim
interface is automatically created on top of that layer 2 interface. The attributes of
the shim interface are inherited from the load-balancing group and cannot be
configured.
All MPLS shim interfaces within a load-balancing group circuit point to the same
MPLS next hop. Traffic arriving from the CE router over this set of MPLS shim
interfaces is merged into a single LSP and sent to the remote PE router.
The VC in label for the layer 2 circuit points to a single ECMP MPLS next hop. The
legs of this ECMP next hop are the member shim interfaces of the load-balancing
group circuit. Consequently, ECMP is used to forward traffic arriving from the core
across the MPLS shim interfaces to the CE router.
Configuring Load-Balancing Groups
You configure Martini circuits with load-balancing groups in a separate mode, in
which the member layer 2 subinterfaces are entered one by one.
For example, the following commands configure two Martini circuits to different PE
routers, in the same load-balancing group 100, sharing the candidate Ethernet ports
2/0 and 3/0:
host1(config)#mpls l2transport load-balancing-group 100 mpls-relay 10.1.1.1 30
host1(config-mpls-l2-group)#member interface fast 2/0.1
host1(config-mpls-l2-group)#member interface fast 3/0.100
host1(config)#mpls l2transport load-balancing-group 100 mpls-relay 10.2.2.2 22
host1(config-mpls-l2-group)#member interface fast 2/0.2
host1(config-mpls-l2-group)#member interface fast 3/0.200
Adding a Member Interface to a Group Circuit
You specify the lower interface as a member interface, as in the following example.
host1(config)#mpls l2transport load-balancing-group 100 mpls-relay 2.2.2.2 202
host1(config-mpls-l2-group)#member interface fast 2/0.500
Removing Member Subinterfaces from a Circuit
To remove a member subinterface from a circuit, either issue the no member
interface command (from the L2 Transport Load-Balancing-Group Configuration
mode) or issue the no mpls-relay command at the VLAN or S-VLAN subinterface
level. Each of the following examples removes member Fast Ethernet subinterface
13/0.2 from the load-balanced Martini circuit:
host1(config)#mpls l2transport load-balancing-group 100 mpls-relay 2.2.2.2 202
Configuring CE-Side Load Balancing for Martini Layer 2 Transport ■ 543
Chapter 7: Configuring Layer 2 Services over MPLS
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